Brush-holder for dynamo-electric machines.



J. H. HOLMES;

BRUSH HOLDER FOR DYNAMO ELECTRIC MACHINES.

APPLICATION FILED JUNE 28, 1913.

1,079,554, Patented Nov. 25,1913.

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JOHN HENRY HOLMES, OF NEWCASTLE-UPON-TYNE, ENGLAND.

BRUSH-HOLDER. FOR DYNAMIC-ELECTRIC MACHINES.

Specification of Letters IPatent.

Patented Nov. 25, 1913.

Application filed June 28, 1913. Serial No. 776,236.

To all whom it may concern:

Be it known that I, J OHN HENRY HOLMES, a subject of the King of Great Britain and Ireland, residing at Portland Road, Newcastle-upon-Tyne, England, have invented a new and useful Improvement in Brush- Holders for Dynamo-Electric Machines, of which the following is a specification.

This invention relates to improvements in brush holders for dynamo electric machines of the type in which the brush slides in a straight sided box or guide and in which there is provided a finger pressing upon the end of the brush causing it tofeed forward as Wear takes place owing to the rubbing action of the brush on the surface of the commutator or slip ring. In such holders it is desirable that the pressure feeding the brush forward should remain as nearly as possible constant throughout the range of movement of the brush in its holder and also that the direction of the pressure should always lie in the central axis of the brush so as to prevent a tendency of the brush to bind in the holder and to bear with unequal pressure upon different portions of the commutator surface which happens to be under the brush at any instant. It is also desirable that the box or guide should be without slots for the passage of the pressure finger so as to maintain as large a conducting surface as possible between the brush and its holder and to prevent uneven wear on the side of the brush.

The object of my invention is to produce a brush holder embodying these desirable features, more especially that relating to the direction of the pressure upon the brush which involves the problem of finding a method whereby the end of the finger shall always bear upon the same central point of the brush throughout the whole working range of the brush in its holder, that is to say the end of the finger must move in a straight line parallel to the sides of the box or guide. The ordinary finger turning around a fixed center or pivot does not accomplish this: The moving end of such finger traverses a curved path.

My invention consists in a pressing finger arrangement which in effect substantially comprises a segment of a wheel of which the center of the wheel acts as the end of the finger which presses upon the brush, and the rim of the wheel acts as the other end of the finger and a substantially straight path parallel to the center line of the brush upon which the said other end of the finger rolls.

In order that the invention may be the better understood, I will now proceed to describe the same in relation to the accompanying drawings, reference being had to the letters and figures marked thereon.

Like letters refer to like parts in the various figures, in which Figure 1 is a side elevation of a brush holder constructed in accordance with my invention. Fig. 2 is a plan view of same to Fig. 1. Fig. 3 is a similar view showing the carbon brush practically worn away. Fig. l shows the pressing finger thrown back into the extreme outermost position for ready access to the brush holder for replacement purposes. Fig. 5 is a side view of the brush finger detached from the holder. Fig. 6 is an end view of the same.

The usual holder lug a is provided for mounting on the ordinary spindle of the rocker and to this lug a is pivotally attached by the screw Z) the brush holder 0. The finger (Z has a pivoted foot 6 to bear on the carbon brush f and transmit the spring pressure. Upon the curved part 9 of the finger (Z struck from center a: lies a flexible strip h which is fixedly attached at its lower end to the finger (Z. This strip h at its upper end has side trunnions i which drop into and engage with notches j in ears is mounted at the top of the part Z which forms the path upon which the curved part 9 rolls. Springs m, adjustable or otherwise, are attached at one end to the holder, and at the other end to a pin a fixed in the finger (Z at such a point that the pull is at one side of the center of the trunnions i when the finger is in the operative position, and on the other side of the said center when in the inoperative position. A handle 0 is rigidly fixed to the back of the finger (Z which serves for manipulating the finger while the tail piece 2) forms a stop to prevent any further backward movement than is indicated in Fig. 4. The pressure on the brush produced by the springs on when in the operative position, remains practically constant owing to the positions of the pins n and the direction of the springs relative to the point of rolling contact.

Although I have described a circular surface for the finger and a straight path for it to roll upon it is obvious I may make such path curved and modify the curved surface of the finger accordingly and further that in substitution of a flexible band I may use toothed surfaces on the finger and path. The finger (Z can be bifurcated as shown in Fig. (3 so as to straddle the part 9.

I am aware that brush holders have been constructed in which the attachment of the spring to the finger and t0 the fixed portion of the holder has been arranged so that the resulting pressure on the finger tip has remained practically constant throughout the range and also that the finger has been shaped so as to avoid as far as possible any necessity to slot the sides of the box, and I make no claim to these features, excepting as combined with the segmental finger substantially as described.

Having thus fully described my invention, I claim as new and desire to secure by Letters Patent 1. In a brush holder for dynamo electric machines of the type in which a rectilineal feeding motion is given to the brush, in combination a pressing finger of curved form, a path fixedly carried on the brush holder on which the curved finger can roll, the curve of the finger and the shape of the path being such that when relative motion takes place between the finger and path, the said finger always presses axially on the brush throughout its whole stroke, a spring or springs adapted to give a feeding pressure to the said finger and restraining means co-acting with the brush holder adapted to act in opposition to said spring or springs to in sure true rolling contact between the curved finger and the path on which it rolls, substantially as described.

2. In a brush holder for dynamo electric machines of the type in which a rectilineal feeding motion is given to the brush, in combination a pressing finger having a curved surface forming part of a circle, a straight line path fixedly carried on the brush holder on which the curved finger can roll, a spring or springs adapted to give a feeding pressure to the said finger and restraining means co-acting with the brush holder adapted to act in opposition to said spring or springs to insure true rolling contact between the curved finger and the path on which it rolls, substantially as described.

3. In a brush holder for dynamo electric machines of the type in which a rectilineal feeding motion is given to the brush, in combination a pressing finger of curved form, a path fixedly carried on the brush holder on which the curved finger can roll, the curve of the finger and the shape of the path being such that when relative motion takes place between the finger and path, the said finger always presses axially on the brush throughout its whole stroke, a spring or springs adapted to give a feeding pressure to the said finger and a flexible restraining strip one end of which is attached to the finger and the other end is attached to the holder so as to allow the finger to roll upon the fixed path while restraining any movement from the spring pressure to destroy the true rolling motion, substantially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

JOHN HENRY HOLMES.

\Vitnesses i G. Hnnnnnrson, J. RonsoN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. C. 

